| Message ID | 20240102091855.70418-1-maimon.sagi@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v5] posix-timers: add multi_clock_gettime system call | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
On Tue, Jan 2, 2024, at 10:18, Sagi Maimon wrote: > Some user space applications need to read some clocks. > Each read requires moving from user space to kernel space. > The syscall overhead causes unpredictable delay between N clocks reads > Removing this delay causes better synchronization between N clocks. > > Introduce a new system call multi_clock_gettime, which can be used to measure > the offset between multiple clocks, from variety of types: PHC, virtual PHC > and various system clocks (CLOCK_REALTIME, CLOCK_MONOTONIC, etc). > The offset includes the total time that the driver needs to read the clock > timestamp. > > New system call allows the reading of a list of clocks - up to PTP_MAX_CLOCKS. > Supported clocks IDs: PHC, virtual PHC and various system clocks. > Up to PTP_MAX_SAMPLES times (per clock) in a single system call read. > The system call returns n_clocks timestamps for each measurement: > - clock 0 timestamp > - ... > - clock n timestamp > > Signed-off-by: Sagi Maimon <maimon.sagi@gmail.com> > --- > Changes since version 4: > - fix error : 'struct __ptp_multi_clock_get' declared inside parameter list > will not be visible outside of this definition or declaration I usually put all the changes for previous versions in a list here, it helps reviewers. The changes you made for previous versions all look good to me, but I think there is still a few things worth considering. I'll also follow up on the earlier threads. > +#define MULTI_PTP_MAX_CLOCKS 32 /* Max number of clocks */ > +#define MULTI_PTP_MAX_SAMPLES 32 /* Max allowed offset measurement samples. */ > + > +struct __ptp_multi_clock_get { > + unsigned int n_clocks; /* Desired number of clocks. */ > + unsigned int n_samples; /* Desired number of measurements per clock. */ > + clockid_t clkid_arr[MULTI_PTP_MAX_CLOCKS]; /* list of clock IDs */ > + /* > + * Array of list of n_clocks clocks time samples n_samples times. > + */ > + struct __kernel_timespec ts[MULTI_PTP_MAX_SAMPLES][MULTI_PTP_MAX_CLOCKS]; > +}; Since you now access each member individually, I think it makes more sense here to just pass these as four register arguments. It helps with argument introspection, avoids a couple of get_user(), and lets you remove the fixed array dimensions. > +SYSCALL_DEFINE1(multi_clock_gettime, struct __ptp_multi_clock_get > __user *, ptp_multi_clk_get) > +{ > + const struct k_clock *kc; > + struct timespec64 *kernel_tp; > + struct timespec64 *kernel_tp_base; > + unsigned int n_clocks; /* Desired number of clocks. */ > + unsigned int n_samples; /* Desired number of measurements per clock. > */ > + unsigned int i, j; > + clockid_t clkid_arr[MULTI_PTP_MAX_CLOCKS]; /* list of clock IDs */ > + int error = 0; > + > + if (copy_from_user(&n_clocks, &ptp_multi_clk_get->n_clocks, > sizeof(n_clocks))) > + return -EFAULT; > + if (copy_from_user(&n_samples, &ptp_multi_clk_get->n_samples, > sizeof(n_samples))) If these remain as struct members rather than register arguments, you should use get_user() instead of copy_from_user(). > + kernel_tp_base = kmalloc_array(n_clocks * n_samples, > + sizeof(struct timespec64), GFP_KERNEL); > + if (!kernel_tp_base) > + return -ENOMEM; To be on the safe side regarding possible data leak, maybe use kcalloc() instead of kmalloc_array() here. > + kernel_tp = kernel_tp_base; > + for (j = 0; j < n_samples; j++) { > + for (i = 0; i < n_clocks; i++) { > + if (put_timespec64(kernel_tp++, (struct __kernel_timespec __user *) > + &ptp_multi_clk_get->ts[j][i])) { I think the typecast here can be removed. Arnd
On Tue, Jan 2, 2024 at 12:22 PM Arnd Bergmann <arnd@arndb.de> wrote: > > On Tue, Jan 2, 2024, at 10:18, Sagi Maimon wrote: > > Some user space applications need to read some clocks. > > Each read requires moving from user space to kernel space. > > The syscall overhead causes unpredictable delay between N clocks reads > > Removing this delay causes better synchronization between N clocks. > > > > Introduce a new system call multi_clock_gettime, which can be used to measure > > the offset between multiple clocks, from variety of types: PHC, virtual PHC > > and various system clocks (CLOCK_REALTIME, CLOCK_MONOTONIC, etc). > > The offset includes the total time that the driver needs to read the clock > > timestamp. > > > > New system call allows the reading of a list of clocks - up to PTP_MAX_CLOCKS. > > Supported clocks IDs: PHC, virtual PHC and various system clocks. > > Up to PTP_MAX_SAMPLES times (per clock) in a single system call read. > > The system call returns n_clocks timestamps for each measurement: > > - clock 0 timestamp > > - ... > > - clock n timestamp > > > > Signed-off-by: Sagi Maimon <maimon.sagi@gmail.com> > > --- > > Changes since version 4: > > - fix error : 'struct __ptp_multi_clock_get' declared inside parameter list > > will not be visible outside of this definition or declaration > > I usually put all the changes for previous versions in a > list here, it helps reviewers. > Will be done on patch V6. > The changes you made for previous versions all look good > to me, but I think there is still a few things worth > considering. I'll also follow up on the earlier threads. > > > +#define MULTI_PTP_MAX_CLOCKS 32 /* Max number of clocks */ > > +#define MULTI_PTP_MAX_SAMPLES 32 /* Max allowed offset measurement samples. */ > > + > > +struct __ptp_multi_clock_get { > > + unsigned int n_clocks; /* Desired number of clocks. */ > > + unsigned int n_samples; /* Desired number of measurements per clock. */ > > + clockid_t clkid_arr[MULTI_PTP_MAX_CLOCKS]; /* list of clock IDs */ > > + /* > > + * Array of list of n_clocks clocks time samples n_samples times. > > + */ > > + struct __kernel_timespec ts[MULTI_PTP_MAX_SAMPLES][MULTI_PTP_MAX_CLOCKS]; > > +}; > > Since you now access each member individually, I think it > makes more sense here to just pass these as four > register arguments. It helps with argument introspection, > avoids a couple of get_user(), and lets you remove the fixed > array dimensions. > I prefer the use of get_user(), I will use it to remove the fixed array dimensions. which will be done on patch V6. > > +SYSCALL_DEFINE1(multi_clock_gettime, struct __ptp_multi_clock_get > > __user *, ptp_multi_clk_get) > > +{ > > + const struct k_clock *kc; > > + struct timespec64 *kernel_tp; > > + struct timespec64 *kernel_tp_base; > > + unsigned int n_clocks; /* Desired number of clocks. */ > > + unsigned int n_samples; /* Desired number of measurements per clock. > > */ > > + unsigned int i, j; > > + clockid_t clkid_arr[MULTI_PTP_MAX_CLOCKS]; /* list of clock IDs */ > > + int error = 0; > > + > > + if (copy_from_user(&n_clocks, &ptp_multi_clk_get->n_clocks, > > sizeof(n_clocks))) > > + return -EFAULT; > > + if (copy_from_user(&n_samples, &ptp_multi_clk_get->n_samples, > > sizeof(n_samples))) > > If these remain as struct members rather than register arguments, > you should use get_user() instead of copy_from_user(). > Will be done on patch V6 > > + kernel_tp_base = kmalloc_array(n_clocks * n_samples, > > + sizeof(struct timespec64), GFP_KERNEL); > > + if (!kernel_tp_base) > > + return -ENOMEM; > > To be on the safe side regarding possible data leak, maybe use > kcalloc() instead of kmalloc_array() here. > Will be done on patch V6. > > + kernel_tp = kernel_tp_base; > > + for (j = 0; j < n_samples; j++) { > > + for (i = 0; i < n_clocks; i++) { > > + if (put_timespec64(kernel_tp++, (struct __kernel_timespec __user *) > > + &ptp_multi_clk_get->ts[j][i])) { > > I think the typecast here can be removed. > You are right, will be fixed on patch V6. > Arnd Thanks for your Notes.
Hi Sagi,
kernel test robot noticed the following build errors:
[auto build test ERROR on tip/x86/asm]
[also build test ERROR on arnd-asm-generic/master tip/timers/core linus/master v6.7-rc8]
[cannot apply to next-20240103]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Sagi-Maimon/posix-timers-add-multi_clock_gettime-system-call/20240102-172105
base: tip/x86/asm
patch link: https://lore.kernel.org/r/20240102091855.70418-1-maimon.sagi%40gmail.com
patch subject: [PATCH v5] posix-timers: add multi_clock_gettime system call
config: csky-randconfig-002-20240104 (https://download.01.org/0day-ci/archive/20240104/202401041000.T0GQPIBW-lkp@intel.com/config)
compiler: csky-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240104/202401041000.T0GQPIBW-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202401041000.T0GQPIBW-lkp@intel.com/
All errors (new ones prefixed by >>):
>> csky-linux-ld: arch/csky/kernel/syscall_table.o:(.data..page_aligned+0x724): undefined reference to `sys_multi_clock_gettime'
On Tue, Jan 02 2024 at 11:18, Sagi Maimon wrote: > Some user space applications need to read some clocks. > Each read requires moving from user space to kernel space. > The syscall overhead causes unpredictable delay between N clocks reads > Removing this delay causes better synchronization between N clocks. As I explained to you before: This is wishful thinking. There is absolutely no guarantee that the syscall will yield better results. It might on average, but that's a useless measure. You also still fail to explain what this is going to solve and how it's used. > Some user space applications need to read some clocks. Is just not an explanation at all. Thanks, tglx
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl index 8cb8bf68721c..9cdeb0bf49db 100644 --- a/arch/x86/entry/syscalls/syscall_64.tbl +++ b/arch/x86/entry/syscalls/syscall_64.tbl @@ -378,6 +378,7 @@ 454 common futex_wake sys_futex_wake 455 common futex_wait sys_futex_wait 456 common futex_requeue sys_futex_requeue +457 common multi_clock_gettime sys_multi_clock_gettime # # Due to a historical design error, certain syscalls are numbered differently diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index fd9d12de7e92..bde7dec493fd 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -74,6 +74,7 @@ struct landlock_ruleset_attr; enum landlock_rule_type; struct cachestat_range; struct cachestat; +struct __ptp_multi_clock_get; #include <linux/types.h> #include <linux/aio_abi.h> @@ -1161,7 +1162,7 @@ asmlinkage long sys_mmap_pgoff(unsigned long addr, unsigned long len, unsigned long prot, unsigned long flags, unsigned long fd, unsigned long pgoff); asmlinkage long sys_old_mmap(struct mmap_arg_struct __user *arg); - +asmlinkage long sys_multi_clock_gettime(struct __ptp_multi_clock_get __user * ptp_multi_clk_get); /* * Not a real system call, but a placeholder for syscalls which are diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h index 756b013fb832..beb3e0052d3c 100644 --- a/include/uapi/asm-generic/unistd.h +++ b/include/uapi/asm-generic/unistd.h @@ -828,9 +828,11 @@ __SYSCALL(__NR_futex_wake, sys_futex_wake) __SYSCALL(__NR_futex_wait, sys_futex_wait) #define __NR_futex_requeue 456 __SYSCALL(__NR_futex_requeue, sys_futex_requeue) +#define __NR_multi_clock_gettime 457 +__SYSCALL(__NR_multi_clock_gettime, sys_multi_clock_gettime) #undef __NR_syscalls -#define __NR_syscalls 457 +#define __NR_syscalls 458 /* * 32 bit systems traditionally used different diff --git a/include/uapi/linux/multi_clock.h b/include/uapi/linux/multi_clock.h new file mode 100644 index 000000000000..5e78dac3a533 --- /dev/null +++ b/include/uapi/linux/multi_clock.h @@ -0,0 +1,21 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +#ifndef _UAPI_MULTI_CLOCK_H +#define _UAPI_MULTI_CLOCK_H + +#include <linux/types.h> +#include <linux/time_types.h> + +#define MULTI_PTP_MAX_CLOCKS 32 /* Max number of clocks */ +#define MULTI_PTP_MAX_SAMPLES 32 /* Max allowed offset measurement samples. */ + +struct __ptp_multi_clock_get { + unsigned int n_clocks; /* Desired number of clocks. */ + unsigned int n_samples; /* Desired number of measurements per clock. */ + clockid_t clkid_arr[MULTI_PTP_MAX_CLOCKS]; /* list of clock IDs */ + /* + * Array of list of n_clocks clocks time samples n_samples times. + */ + struct __kernel_timespec ts[MULTI_PTP_MAX_SAMPLES][MULTI_PTP_MAX_CLOCKS]; +}; + +#endif /* _UAPI_MULTI_CLOCK_H */ diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c index b924f0f096fa..1d321dc56a25 100644 --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -31,6 +31,8 @@ #include <linux/compat.h> #include <linux/nospec.h> #include <linux/time_namespace.h> +#include <linux/multi_clock.h> +#include <linux/slab.h> #include "timekeeping.h" #include "posix-timers.h" @@ -1426,6 +1428,63 @@ SYSCALL_DEFINE4(clock_nanosleep_time32, clockid_t, which_clock, int, flags, #endif +SYSCALL_DEFINE1(multi_clock_gettime, struct __ptp_multi_clock_get __user *, ptp_multi_clk_get) +{ + const struct k_clock *kc; + struct timespec64 *kernel_tp; + struct timespec64 *kernel_tp_base; + unsigned int n_clocks; /* Desired number of clocks. */ + unsigned int n_samples; /* Desired number of measurements per clock. */ + unsigned int i, j; + clockid_t clkid_arr[MULTI_PTP_MAX_CLOCKS]; /* list of clock IDs */ + int error = 0; + + if (copy_from_user(&n_clocks, &ptp_multi_clk_get->n_clocks, sizeof(n_clocks))) + return -EFAULT; + if (copy_from_user(&n_samples, &ptp_multi_clk_get->n_samples, sizeof(n_samples))) + return -EFAULT; + if (n_samples > MULTI_PTP_MAX_SAMPLES) + return -EINVAL; + if (n_clocks > MULTI_PTP_MAX_CLOCKS) + return -EINVAL; + if (copy_from_user(clkid_arr, &ptp_multi_clk_get->clkid_arr, + sizeof(clockid_t) * n_clocks)) + return -EFAULT; + + kernel_tp_base = kmalloc_array(n_clocks * n_samples, + sizeof(struct timespec64), GFP_KERNEL); + if (!kernel_tp_base) + return -ENOMEM; + + kernel_tp = kernel_tp_base; + for (j = 0; j < n_samples; j++) { + for (i = 0; i < n_clocks; i++) { + kc = clockid_to_kclock(clkid_arr[i]); + if (!kc) { + error = -EINVAL; + goto out; + } + error = kc->clock_get_timespec(clkid_arr[i], kernel_tp++); + if (error) + goto out; + } + } + + kernel_tp = kernel_tp_base; + for (j = 0; j < n_samples; j++) { + for (i = 0; i < n_clocks; i++) { + if (put_timespec64(kernel_tp++, (struct __kernel_timespec __user *) + &ptp_multi_clk_get->ts[j][i])) { + error = -EFAULT; + goto out; + } + } + } +out: + kfree(kernel_tp_base); + return error; +} + static const struct k_clock clock_realtime = { .clock_getres = posix_get_hrtimer_res, .clock_get_timespec = posix_get_realtime_timespec,
Some user space applications need to read some clocks. Each read requires moving from user space to kernel space. The syscall overhead causes unpredictable delay between N clocks reads Removing this delay causes better synchronization between N clocks. Introduce a new system call multi_clock_gettime, which can be used to measure the offset between multiple clocks, from variety of types: PHC, virtual PHC and various system clocks (CLOCK_REALTIME, CLOCK_MONOTONIC, etc). The offset includes the total time that the driver needs to read the clock timestamp. New system call allows the reading of a list of clocks - up to PTP_MAX_CLOCKS. Supported clocks IDs: PHC, virtual PHC and various system clocks. Up to PTP_MAX_SAMPLES times (per clock) in a single system call read. The system call returns n_clocks timestamps for each measurement: - clock 0 timestamp - ... - clock n timestamp Signed-off-by: Sagi Maimon <maimon.sagi@gmail.com> --- Changes since version 4: - fix error : 'struct __ptp_multi_clock_get' declared inside parameter list will not be visible outside of this definition or declaration arch/x86/entry/syscalls/syscall_64.tbl | 1 + include/linux/syscalls.h | 3 +- include/uapi/asm-generic/unistd.h | 4 +- include/uapi/linux/multi_clock.h | 21 +++++++++ kernel/time/posix-timers.c | 59 ++++++++++++++++++++++++++ 5 files changed, 86 insertions(+), 2 deletions(-) create mode 100644 include/uapi/linux/multi_clock.h